This invention relates to an electronic musical instrument, and more particularly to a method and apparatus for generating electronic waveforms whose amplitudes and harmonic structure may vary with time.
In the past, signal generators for electronic organs and the like have used frequency dividers and filters with one or more oscillators to generate scales of musical notes. In some cases, phase-locked loops have been used as frequency multipliers to facilitate generating the desired tone intervals. Such signal generators have generally been limited to producing sinusoidal or sawtooth waveforms of a controlled amplitude. Alternatively, waveforms of other forms have been generated using waveform data stored as a table in a memory of a computer. While good tones have been produced, they lacked, for example, the facility for introducing attack in addition to carefully controlled harmonics for desired timbres in synthesizing musical sounds of particular instruments.
What is required is a system for generating with greater flexibility more varied waveforms under digital control which may be mixed in different ways in order to synthesize the sounds of such varied musical instruments as reed, wind and string, and to generate still other musical sounds distinct from known instruments.